Shared nack resource for groupcast and multicast in new radio v2x communications

ABSTRACT

Various examples and schemes pertaining to shared negative acknowledgement (NACK) for groupcast and multicast in New Radio (NR) vehicle-to-everything (V2X) communications are described. An apparatus as a source user equipment (UE) transmits data to two or more destination UEs of a plurality of destination UEs via groupcast or multicast with hybrid automatic repeat request (HARQ). The apparatus then receives a NACK on a single time-frequency resource from at least one of the two or more destination UEs. The single time-frequency resource is shared by the plurality of destination UEs to transmit the NACK to the source UE.

CROSS REFERENCE TO RELATED PATENT APPLICATION(S)

The present disclosure is part of a non-provisional application claiming the priority benefit of U.S. Patent Application No. 62/738,017, filed on 28 Sep. 2018, the content of which being incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure is generally related to wireless communications and, more particularly, to shared negative acknowledgement (NACK) for groupcast and multicast in New Radio (NR) vehicle-to-everything (V2X) communications.

BACKGROUND

Unless otherwise indicated herein, approaches described in this section are not prior art to the claims listed below and are not admitted as prior art by inclusion in this section.

Under the 3rd Generation Partnership Project (3GPP) specifications, vehicle platooning can support reliable vehicle-to-vehicle (V2V) communications between a specific user equipment (UE) supporting V2X applications and up to nineteen other UEs supporting V2X applications. Moreover, under the 3GPP specifications, groupcast and multicast with hybrid automatic repeat request (HARQ) is supported in NR V2X communications. That is, when a source UE transmits data to a group of destination UEs, each of the destination UEs can inform the source UE whether the data has been successfully received or not. The feedback mechanism for HARQ is straightforward and typically involves each destination/receiving UE to transmit an acknowledgement (ACK) or NACK to the source UE through a dedicated time-frequency resource. For groupcast and multicast, this means the required amount of resources for feedback is proportional to the number of destination/receiving UEs. However, this could result in excessive overhead and inefficiency use of available bandwidth, thereby decreasing overall system performance.

SUMMARY

The following summary is illustrative only and is not intended to be limiting in any way. That is, the following summary is provided to introduce concepts, highlights, benefits and advantages of the novel and non-obvious techniques described herein. Selected implementations are further described below in the detailed description. Thus, the following summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter.

In one aspect, a method may involve a processor of an apparatus, as a source UE, transmitting data to two or more destination UEs of a plurality of destination UEs via groupcast or multicast with HARQ. The method may also involve the processor receiving a NACK on a single time-frequency resource from at least one of the two or more destination UEs. The single time-frequency resource may be shared by the plurality of destination UEs to transmit the NACK to the source UE.

In one aspect, a method may involve a processor of an apparatus, as a destination UE, receiving data from a source UE via groupcast or multicast with HARQ. The method may also involve the processor transmitting a NACK on a single time-frequency resource to the source UE. The single time-frequency resource may be shared by the plurality of destination UEs to transmit the NACK to the source UE.

In one aspect, an apparatus may include a communication device and a processor coupled to the communication device. The communication device may be configured to wirelessly communicate with a network. The processor may be configured to transmit, via the communication device and as a source UE, data to two or more destination UEs of a plurality of destination UEs via groupcast or multicast with HARQ. The processor may also be configured to receive, via the communication device, a NACK on a single time-frequency resource from at least one of the two or more destination UEs. The single time-frequency resource may be shared by the plurality of destination UEs to transmit the NACK to the source UE.

It is noteworthy that, although description provided herein may be in the context of certain radio access technologies, networks and network topologies such as NR V2X and V2V, the proposed concepts, schemes and any variation(s)/derivative(s) thereof may be implemented in, for and by other types of radio access technologies, networks and network topologies such as, for example and without limitation, 5^(th) Generation (5G), Long-Term Evolution (LTE), LTE-Advanced, LTE-Advanced Pro and any future-developed networks and technologies. Thus, the scope of the present disclosure is not limited to the examples described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of the present disclosure. The drawings illustrate implementations of the disclosure and, together with the description, serve to explain the principles of the disclosure. It is appreciable that the drawings are not necessarily in scale as some components may be shown to be out of proportion than the size in actual implementation in order to clearly illustrate the concept of the present disclosure.

FIG. 1 is a diagram of an example network environment in which various solutions and schemes in accordance with the present disclosure may be implemented.

FIG. 2 is a diagram of an example scenario in accordance with the present disclosure.

FIG. 3 is a diagram of an example scenario in accordance with the present disclosure.

FIG. 4 is a diagram of an example scenario in accordance with the present disclosure.

FIG. 5 is a block diagram of an example communication environment in which various solutions and schemes in accordance with the present disclosure may be implemented.

FIG. 6 is a flowchart of an example process in accordance with an implementation of the present disclosure.

FIG. 7 is a flowchart of an example process in accordance with an implementation of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATIONS

Detailed embodiments and implementations of the claimed subject matters are disclosed herein. However, it shall be understood that the disclosed embodiments and implementations are merely illustrative of the claimed subject matters which may be embodied in various forms. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments and implementations set forth herein. Rather, these exemplary embodiments and implementations are provided so that description of the present disclosure is thorough and complete and will fully convey the scope of the present disclosure to those skilled in the art. In the description below, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments and implementations.

Overview

Implementations in accordance with the present disclosure relate to various techniques, methods, schemes and/or solutions pertaining to shared NACK for groupcast and multicast in NR V2X communications. According to the present disclosure, a number of possible solutions may be implemented separately or jointly. That is, although these possible solutions may be described below separately, two or more of these possible solutions may be implemented in one combination or another.

FIG. 1 illustrates an example network environment 100 in which various solutions and schemes in accordance with the present disclosure may be implemented. Each of FIG. 2, FIG. 3 and FIG. 4 illustrates an example scenario 200, example scenario 300 and scenario 400, respectively, in accordance with the present disclosure. Each of scenario 200, scenario 300 and scenario 400 may be implemented in network environment 100. The following description of various proposed schemes is provided with reference to FIG. 1˜FIG. 4.

Referring to FIG. 1, network environment 100 may involve a source UE 110 in wireless communication with a plurality of destination UEs 120(1)˜120(N), with N being a positive integer greater than 1, that together may form an NR V2X communication network. That is, each of source UE 110 and destination UEs 120(1)˜120N) may be in or as a part of, for example and without limitation, a vehicle, a roadside unit (RSU) (e.g., a traffic signal, a street lamp, a roadside sensor or a roadside structure), a portable device (e.g., smartphone) or an Internet of Thing (IoT). In network environment 100, source UE 110 and destination UEs 120(1)˜120N) may implement various schemes pertaining to NACK for groupcast and multicast in NR V2X communications in accordance with the present disclosure.

With the conventional HARQ mechanism for ACK/NACK feedback, it is straightforward for unicast (one-to-one) communication but, for groupcast and multicast, the required amount of resources would be proportional to the number of receiving/destination UEs. It is noteworthy that, for some use cases, it may suffice for a source UE (e.g., source UE 110) to learn whether to perform a retransmission based on certain factors. Firstly, it may not be critical to know which specific destination UE has a decoding failure of the data channel. Secondly, there may be no need to tackle the situation where some destination UEs cannot decode the control channel. Accordingly, a proposed scheme in accordance with the present disclosure aims to use minimum sufficient feedback resource.

Under the proposed scheme, a single time-frequency resource (e.g., Physical Sidelink Feedback Channel (PSFCH)) may be allocated for feedback, with the single time-frequency resource shared by all the destination UEs 120(1)˜120(N). Under the proposed scheme, when a destination UE fails to decode the data channel, it may transmit a NACK on the shared time-frequency resource to notify source UE 110 that data transmitted via groupcast and/or multicast has not been successfully decoded by such a destination UE. Otherwise, when the decoding of the data channel is successful, each destination UE would take no action in terms of providing feedback to source UE 110 (i.e., transmitting no ACK to source UE 110). Moreover, under the proposed scheme, a signal or sequence of the NACK may be the same for all destination UEs 120(1)˜120(N). Furthermore, under the proposed scheme, source UE 110 may detect the received power level of the NACK signal or sequence on the shared time-frequency resource. In an event that the received power level is higher than a predetermined threshold, source UE 110 may perform a retransmission when a maximum number of transmissions (including retransmissions) has not been reached. Otherwise, in an event that the maximum number of transmissions has been reached, source UE 110 may not perform a retransmission even when the received power level is higher than the predetermined threshold.

Referring to FIG. 2, in scenario 200, each of destination UEs 120(1)˜120(N) (denoted as UE 1, UE 2, UE 3 and UE 4 in FIG. 2) may respectively experience success or failure in decoding data transmitted by source UE 110 via groupcast and/or multicast. In the example shown in FIG. 2, each of UE 1 and UE 3 succeeded in decoding the data while each of UE 2 and UE 4 failed in decoding the data. Accordingly, neither UE 1 nor UE 3 would transmit an ACK to source UE 110. On the other hand, each of UE 2 and UE 4 would transmit a NACK (each denoted as SNACK in FIG. 2) to source UE 110 on the shared time-frequency resource. The signal detected by source UE 110 (denoted as y_(NACK) in FIG. 2) may be a combination of the NACK from both UE 2 and UE 4, with channel response (H₂+H₄) and noise (z_(NACK)).

Referring to FIG. 3, in scenario 300, a concept of group size-dependent threshold is illustrated. Under a proposed scheme in accordance with the present disclosure, when relaying is enabled, a receiving (Rx) UE (e.g., one of the destination UEs 120(1)˜120(N)) may forward packets received from a transmitting (Tx) UE (e.g., UE 110) to one or more other Rx UEs (e.g., one or more other destination UEs 120(1)˜120(N)), and the Tx UE would merely need to ensure that nearby Rx UEs have successfully received the packets. Due to high mobility, it tends to be difficult to have all Rx UEs within a communication coverage of the Tx UE. For illustrative purposes, as shown in FIG. 3, while a group of Rx UEs (e.g., 9 Rx UEs shown in FIG. 3) are within the physical sidelink control channel (PSCCH) coverage or the Tx UE, due to mobility and/or distance only a subset of the group of Rx UEs (e.g., 5 Rx UEs) are within the physical sidelink shared channel (PSSCH) coverage of the Tx UE. In an event that the received power of HARQ NACK is small, the Tx UE may assume that one or more distant Rx UE(s) have successfully received the packets and thus can help relay the packets.

Under the proposed scheme, with the transmit power of the Tx UE adjusted to achieve a PSSCH coverage of roughly (100−x) % of the Rx UEs, the remaining x % of the Rx UEs may have a lower block error rate (BLER). Any of the x % of the Rx UEs with successful decoding of the received packets may serve as a relaying UE.

Under the proposed scheme, the Tx UE may estimate the received power of HARQ NACK (herein denoted as P) sent by one Rx UE at the boundary of PSCCH coverage. Accordingly, a group-size dependent threshold may be set as α

max(x %×N×P, P), with N denoting the size of the group. For more accuracy, difference in path loss among different UEs may be considered in the threshold formula. Nevertheless, the threshold may serve as a lower bound and thus may be more robust with respect to estimation error. In short, under the proposed scheme, the threshold for the total received power of ACK and NACK may depend on or otherwise be related to the number of Rx UEs (e.g., number of destination UEs 120(1)˜120(N)).

Referring to FIG. 4, in scenario 400, the concept of group size-dependent threshold is further illustrated. As an example, with x=50, N=10, then α=5P. For convenience of exposition, it may be assumed that the received power from every Rx UE is P. Then, the implementation of threshold may be equivalent to counting the number of failed Rx UEs. Part (A) of FIG. 4 illustrates an example instance of HARQ retransmission being not required. In this example, 3 out of the 9 Rx UEs within the PSCCH coverage experience failure in decoding the packets and, thus, the total received power in this example is 3P. Part (B) of FIG. 4 illustrates an example instance of HARQ retransmission being required. In this example, 6 out of the 9 Rx UEs within the PSCCH coverage experience failure in decoding the packets and, thus, the total received power in this example is 6P.

Illustrative Implementations

FIG. 5 illustrates an example communication environment 500 having an example apparatus 510 and an example apparatus 520 in accordance with an implementation of the present disclosure. Each of apparatus 510 and apparatus 520 may perform various functions to implement schemes, techniques, processes and methods described herein pertaining to shared NACK for groupcast and multicast in NR V2X communications, including various schemes described above as well as processes 600 and 700 described below.

Each of apparatus 510 and apparatus 520 may be a part of an electronic apparatus, which may be a UE such as a vehicle, a portable or mobile apparatus, a wearable apparatus, a wireless communication apparatus or a computing apparatus. For instance, each of apparatus 510 and apparatus 520 may be implemented in an electronic control unit (ECU) of a vehicle, a smartphone, a smartwatch, a personal digital assistant, a digital camera, or a computing equipment such as a tablet computer, a laptop computer or a notebook computer. Each of apparatus 510 and apparatus 520 may also be a part of a machine type apparatus, which may be an IoT or NB-IoT apparatus such as an immobile or a stationary apparatus, a home apparatus, a wire communication apparatus or a computing apparatus. For instance, each of apparatus 510 and apparatus 520 may be implemented in a smart thermostat, a smart fridge, a smart door lock, a wireless speaker or a home control center. Alternatively, each of apparatus 510 and apparatus 520 may be implemented in the form of one or more integrated-circuit (IC) chips such as, for example and without limitation, one or more single-core processors, one or more multi-core processors, or one or more complex-instruction-set-computing (CISC) processors. Each of apparatus 510 and apparatus 520 may include at least some of those components shown in FIG. 5 such as a processor 512 and a processor 522, respectively. Each of apparatus 510 and apparatus 520 may further include one or more other components not pertinent to the proposed scheme of the present disclosure (e.g., internal power supply, display device and/or user interface device), and, thus, such component(s) of each of apparatus 510 and apparatus 520 are neither shown in FIG. 5 nor described below in the interest of simplicity and brevity.

In some implementations, at least one of apparatus 510 and apparatus 520 may be a part of an electronic apparatus, which may be a vehicle, a roadside unit (RSU), network node or base station (e.g., eNB, gNB or TRP), a small cell, a router or a gateway. For instance, at least one of apparatus 510 and apparatus 520 may be implemented in a vehicle in a V2V or V2X network, an eNodeB in an LTE, LTE-Advanced or LTE-Advanced Pro network or in a gNB in a 5G, NR, IoT or NB-IoT network. Alternatively, at least one of apparatus 510 and apparatus 520 may be implemented in the form of one or more IC chips such as, for example and without limitation, one or more single-core processors, one or more multi-core processors, or one or more CISC processors.

In one aspect, each of processor 512 and processor 522 may be implemented in the form of one or more single-core processors, one or more multi-core processors, or one or more CISC processors. That is, even though a singular term “a processor” is used herein to refer to processor 512 and processor 522, each of processor 512 and processor 522 may include multiple processors in some implementations and a single processor in other implementations in accordance with the present disclosure. In another aspect, each of processor 512 and processor 522 may be implemented in the form of hardware (and, optionally, firmware) with electronic components including, for example and without limitation, one or more transistors, one or more diodes, one or more capacitors, one or more resistors, one or more inductors, one or more memristors and/or one or more varactors that are configured and arranged to achieve specific purposes in accordance with the present disclosure. In other words, in at least some implementations, each of processor 512 and processor 522 is a special-purpose machine specifically designed, arranged and configured to perform specific tasks including shared NACK for groupcast and multicast in NR V2X communications in accordance with various implementations of the present disclosure.

In some implementations, apparatus 510 may also include a transceiver 516, as a communication device, coupled to processor 512 and capable of wirelessly transmitting and receiving data. In some implementations, apparatus 510 may further include a memory 514 coupled to processor 512 and capable of being accessed by processor 512 and storing data therein. In some implementations, apparatus 520 may also include a transceiver 526, as a communication device, coupled to processor 522 and capable of wirelessly transmitting and receiving data. In some implementations, apparatus 520 may further include a memory 524 coupled to processor 522 and capable of being accessed by processor 522 and storing data therein. Accordingly, apparatus 510 and apparatus 520 may wirelessly communicate with each other via transceiver 516 and transceiver 526, respectively.

To aid better understanding, the following description of the operations, functionalities and capabilities of each of apparatus 510 and apparatus 520 is provided in the context of a NR V2X communication environment in which apparatus 510 is implemented in or as a wireless communication device, a communication apparatus or a UE and apparatus 520 is implemented in or as a network node (e.g., base station) connected or otherwise communicatively coupled to a wireless network (e.g., wireless network).

In one aspect of shared NACK for groupcast and multicast in NR V2X communications in accordance with the present disclosure, processor 512 of apparatus 510, as a source UE, may transmit, via transceiver 516, data to two or more destination UEs of a plurality of destination UEs (including apparatus 520) via groupcast or multicast with HARQ. Moreover, processor 512 may receive, via transceiver 516, a NACK on a single time-frequency resource from at least one of the two or more destination UEs (e.g., apparatus 520). The single time-frequency resource may be shared by the plurality of destination UEs to transmit the NACK to apparatus 310.

In some implementations, in receiving the NACK, processor 512 may receive the NACK in response to at least one of the two or more destination UEs failing to decode the data. Moreover, processor 512 may receive no ACK in response to each of the two or more destination UEs successfully decoding the data.

In some implementations, a signal or sequence of the NACK may be same for all of the plurality of destination UEs. That is, all the destination UEs may transmit the NACK using the same signal or sequence on the shared time-frequency resource.

In some implementations, in receiving the NACK, processor 512 may detect a signal or sequence of the NACK on the single time-frequency resource.

In some implementations, processor 512 may perform additional operations. For instance, processor 512 may perform, via transceiver 516, a retransmission of the data in response to a received power level of a signal or sequence of the NACK exceeding a predetermined threshold. In some implementations, in performing the retransmission of the data, processor 512 performing certain operations. For instance, processor 512 may determine whether a maximum number of transmissions of the data has been reached. Moreover, processor 512 may perform the retransmission of the data responsive to: (1) the received power level of the signal or sequence of the NACK exceeding the predetermined threshold, and (2) the maximum number of transmissions of the data having not been reached.

In some implementations, in transmitting and receiving, processor 512 may transmit and receive in compliance with an NR V2X communication specification.

In some implementations, a threshold for a total received power of NACK received from the plurality of destination UEs is related to a number of UEs among the plurality of destination UEs.

In another aspect of shared NACK for groupcast and multicast in NR V2X communications in accordance with the present disclosure, processor 522 of apparatus 520, as a destination UE a plurality of destination UEs, may receive, via transceiver 526, data from a source UE (e.g., apparatus 510) via groupcast or multicast with HARQ. Moreover, processor 522 may transmit, via transceiver 526, a NACK on a single time-frequency resource to the source UE. The single time-frequency resource may be shared by the plurality of destination UEs to transmit the NACK to apparatus 510 as the source UE.

In some implementations, in transmitting the NACK processor 522 may transmit the NACK in response to a failure in decoding the data. Moreover, processor 522 may transmit no ACK in response to a success in decoding the data.

In some implementations, a signal or sequence of the NACK may be same for all of the plurality of destination UEs. That is, all the destination UEs, including apparatus 520, may transmit the NACK using the same signal or sequence on the shared time-frequency resource.

In some implementations, processor 522 may perform additional operations. For instance, processor 522 may receive, via transceiver 526, a retransmission of the data in response to a power level of a signal or sequence of the NACK received by apparatus 510 exceeding a predetermined threshold. In some implementations, in receiving the retransmission of the data, process 700 may involve processor 522 receiving the retransmission of the data in response to: (1) the power level of the signal or sequence of the NACK received by apparatus 510 exceeding the predetermined threshold, and (2) a maximum number of transmissions of the data by apparatus 510 having not been reached.

In some implementations, in receiving and transmitting processor 522 may receive and transmit in compliance with an NR V2X communication specification.

In some implementations, a threshold for a total received power of NACK received from the plurality of destination UEs is related to a number of UEs among the plurality of destination UEs.

Illustrative Processes

FIG. 6 illustrates an example process 600 in accordance with an implementation of the present disclosure. Process 600 may be an example implementation of the proposed schemes described above with respect to shared NACK for groupcast and multicast in NR V2X communications in accordance with the present disclosure. Process 600 may represent an aspect of implementation of features of apparatus 510 and apparatus 520. Process 600 may include one or more operations, actions, or functions as illustrated by one or more of blocks 610 and 620. Although illustrated as discrete blocks, various blocks of process 600 may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. Moreover, the blocks of process 600 may be executed in the order shown in FIG. 6 or, alternatively, in a different order. Process 600 may also be repeated partially or entirely. Process 600 may be implemented by apparatus 510, apparatus 520 and/or any suitable wireless communication device, UE, roadside unit (RUS), base station or machine type devices. Solely for illustrative purposes and without limitation, process 600 is described below in the context of apparatus 510 as a source UE (e.g., UE 110) and apparatus 520 as a destination UE (e.g., UE 120(1)) of a plurality of destination UEs (e.g., UE 120(1)˜UE 120(N) in network environment 100). Process 600 may begin at block 610.

At 610, process 600 may involve processor 512 of apparatus 510, as a source UE, transmitting, via transceiver 516, data to two or more destination UEs of a plurality of destination UEs (including apparatus 520) via groupcast or multicast with HARQ. Process 600 may proceed from 610 to 620.

At 620, process 600 may involve processor 512 receiving, via transceiver 516, a NACK on a single time-frequency resource from at least one of the two or more destination UEs (e.g., apparatus 520). The single time-frequency resource may be shared by the plurality of destination UEs to transmit the NACK to apparatus 510.

In some implementations, in receiving the NACK, process 600 may involve processor 512 receiving the NACK in response to at least one of the two or more destination UEs failing to decode the data. Moreover, process 600 may involve processor 512 receiving no ACK in response to each of the two or more destination UEs successfully decoding the data.

In some implementations, a signal or sequence of the NACK may be same for all of the plurality of destination UEs. That is, all the destination UEs may transmit the NACK using the same signal or sequence on the shared time-frequency resource.

In some implementations, in receiving the NACK, process 600 may involve processor 512 detecting a signal or sequence of the NACK on the single time-frequency resource.

In some implementations, process 600 may involve processor 512 performing additional operations. For instance, process 600 may involve processor 512 performing, via transceiver 516, a retransmission of the data in response to a received power level of a signal or sequence of the NACK exceeding a predetermined threshold. In some implementations, in performing the retransmission of the data, process 600 may involve processor 512 performing certain operations. For instance, process 600 may involve processor 512 determining whether a maximum number of transmissions of the data has been reached. Moreover, process 600 may involve processor 512 performing the retransmission of the data responsive to: (1) the received power level of the signal or sequence of the NACK exceeding the predetermined threshold, and (2) the maximum number of transmissions of the data having not been reached.

In some implementations, in transmitting and receiving, process 600 may involve processor 512 transmitting and receiving in compliance with an NR V2X communication specification.

In some implementations, a threshold for a total received power of NACK received from the plurality of destination UEs is related to a number of UEs among the plurality of destination UEs.

FIG. 7 illustrates an example process 700 in accordance with an implementation of the present disclosure. Process 700 may be an example implementation of the proposed schemes described above with respect to shared NACK for groupcast and multicast in NR V2X communications in accordance with the present disclosure. Process 700 may represent an aspect of implementation of features of apparatus 510 and apparatus 520. Process 700 may include one or more operations, actions, or functions as illustrated by one or more of blocks 710 and 720. Although illustrated as discrete blocks, various blocks of process 700 may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. Moreover, the blocks of process 700 may executed in the order shown in FIG. 7 or, alternatively, in a different order. Process 700 may also be repeated partially or entirely. Process 500 may be implemented by apparatus 510, apparatus 520 and/or any suitable wireless communication device, UE, roadside unit (RUS), base station or machine type devices. Solely for illustrative purposes and without limitation, process 700 is described below in the context of apparatus 510 as a source UE (e.g., UE 110) and apparatus 520 as a destination UE (e.g., UE 120(1)) of a plurality of destination UEs (e.g., UE 120(1)˜UE 120(N) in network environment 100). Process 700 may begin at block 710.

At 710, process 700 may involve processor 522 of apparatus 520, as a destination UE a plurality of destination UEs, receiving, via transceiver 526, data from a source UE (e.g., apparatus 510) via groupcast or multicast with HARQ. Process 700 may proceed from 710 to 720.

At 720, process 700 may involve processor 522 transmitting, via transceiver 526, a NACK on a single time-frequency resource to the source UE. The single time-frequency resource may be shared by the plurality of destination UEs to transmit the NACK to the source UE.

In some implementations, in transmitting the NACK, process 700 may involve processor 522 transmitting the NACK in response to a failure in decoding the data. Moreover, process 700 may involve processor 522 transmitting no ACK in response to a success in decoding the data.

In some implementations, a signal or sequence of the NACK may be same for all of the plurality of destination UEs. That is, all the destination UEs, including apparatus 520, may transmit the NACK using the same signal or sequence on the shared time-frequency resource.

In some implementations, process 700 may involve processor 522 performing additional operations. For instance, process 700 may involve processor 522 receiving, via transceiver 526, a retransmission of the data in response to a power level of a signal or sequence of the NACK received by the source UE exceeding a predetermined threshold. In some implementations, in receiving the retransmission of the data, process 700 may involve processor 522 receiving the retransmission of the data in response to: (1) the power level of the signal or sequence of the NACK received by the source UE exceeding the predetermined threshold, and (2) a maximum number of transmissions of the data by the source UE having not been reached.

In some implementations, in receiving and transmitting, process 700 may involve processor 522 receiving and transmitting in compliance with an NR V2X communication specification.

In some implementations, a threshold for a total received power of NACK received from the plurality of destination UEs is related to a number of UEs among the plurality of destination UEs.

Additional Notes

The herein-described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely examples, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled”, to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable”, to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

Further, with respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

Moreover, it will be understood by those skilled in the art that, in general, terms used herein, and especially in the appended claims, e.g., bodies of the appended claims, are generally intended as “open” terms, e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc. It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to implementations containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an,” e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more;” the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number, e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations. Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention, e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc. In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention, e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc. It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

From the foregoing, it will be appreciated that various implementations of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various implementations disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

1. A method, comprising: transmitting, by a processor of an apparatus as a source user equipment (UE), data to two or more destination UEs of a plurality of destination UEs via groupcast or multicast with hybrid automatic repeat request (HARQ); and receiving, by the processor, a negative acknowledgement (NACK) on a single time-frequency resource from at least one of the two or more destination UEs, wherein the single time-frequency resource is shared by the plurality of destination UEs to transmit the NACK to the source UE.
 2. The method of claim 1, wherein the receiving of the NACK comprises: receiving the NACK responsive to at least one of the two or more destination UEs failing to decode the data; and receiving no acknowledgement (ACK) responsive to each of the two or more destination UEs successfully decoding the data.
 3. The method of claim 1, wherein a signal or sequence of the NACK is same for all of the plurality of destination UEs.
 4. The method of claim 1, wherein the receiving of the NACK comprises detecting a signal or sequence of the NACK on the single time-frequency resource.
 5. The method of claim 1, further comprising: performing, by the processor, a retransmission of the data responsive to a received power level of a signal or sequence of the NACK exceeding a predetermined threshold.
 6. The method of claim 5, wherein the performing of the retransmission of the data comprises: determining whether a maximum number of transmissions of the data has been reached; and performing the retransmission of the data responsive to: the received power level of the signal or sequence of the NACK exceeding the predetermined threshold; and the maximum number of transmissions of the data having not been reached.
 7. The method of claim 1, wherein a threshold for a total received power of negative acknowledgement (NACK) received from the plurality of destination UEs is related to a number of UEs among the plurality of destination UEs.
 8. A method, comprising: receiving, by a processor of an apparatus as a destination user equipment (UE) of a plurality of destination UEs, data from a source UE via groupcast or multicast with hybrid automatic repeat request (HARQ); and transmitting, by the processor, a negative acknowledgement (NACK) on a single time-frequency resource to the source UE, wherein the single time-frequency resource is shared by the plurality of destination UEs to transmit the NACK to the source UE.
 9. The method of claim 8, wherein the transmitting of the NACK comprises: transmitting the NACK responsive to a failure in decoding the data; and transmitting no acknowledgement (ACK) responsive to a success in decoding the data.
 10. The method of claim 8, wherein a signal or sequence of the NACK is same for all of the plurality of destination UEs.
 11. The method of claim 8, further comprising: receiving, by the processor, a retransmission of the data responsive to a power level of a signal or sequence of the NACK received by the source UE exceeding a predetermined threshold.
 12. The method of claim 11, wherein the receiving of the retransmission of the data comprises receiving the retransmission of the data responsive to: the power level of the signal or sequence of the NACK received by the source UE exceeding the predetermined threshold; and a maximum number of transmissions of the data by the source UE having not been reached.
 13. The method of claim 8, wherein a threshold for a total received power of negative acknowledgement (NACK) received from the plurality of destination UEs is related to a number of UEs among the plurality of destination UEs.
 14. An apparatus, comprising: a communication device configured to wirelessly communicate with a network; and a processor coupled to the communication device and configured to perform operations comprising: transmitting, via the communication device and as a source user equipment (UE), data to two or more destination UEs of a plurality of destination UEs via groupcast or multicast with hybrid automatic repeat request (HARQ); and receiving, via the communication device, a negative acknowledgement (NACK) on a single time-frequency resource from at least one of the two or more destination UEs, wherein the single time-frequency resource is shared by the plurality of destination UEs to transmit the NACK to the source UE.
 15. The apparatus of claim 14, wherein, in receiving the NACK, the processor is configured to perform operations comprising: receiving the NACK responsive to at least one of the two or more destination UEs failing to decode the data; and receiving no acknowledgement (ACK) responsive to each of the two or more destination UEs successfully decoding the data.
 16. The apparatus of claim 14, wherein a signal or sequence of the NACK is same for all of the plurality of destination UEs.
 17. The apparatus of claim 14, wherein, in receiving the NACK, the processor is configured to detect a signal or sequence of the NACK on the single time-frequency resource.
 18. The apparatus of claim 14, wherein the processor is further configured to perform operations comprising: performing a retransmission of the data responsive to a received power level of a signal or sequence of the NACK exceeding a predetermined threshold.
 19. The apparatus of claim 18, wherein, in performing the retransmission of the data, the processor is configured to perform operations comprising: determining whether a maximum number of transmissions of the data has been reached; and performing the retransmission of the data responsive to: the received power level of the signal or sequence of the NACK exceeding the predetermined threshold; and the maximum number of transmissions of the data having not been reached.
 20. The apparatus of claim 14, wherein a threshold for a total received power of negative acknowledgement (NACK) received from plurality of destination UEs is related to a number of UEs among the plurality of destination UEs. 